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Research Papers: Gas Turbines: Structures and Dynamics

Rotor Model Updating and Validation for an Active Magnetic Bearing Based High-Speed Machining Spindle

[+] Author and Article Information
Jerzy T. Sawicki

Fellow ASME

Alexander H. Pesch

Center for Rotating Machinery Dynamics and Control (RoMaDyC),
Cleveland State University,
Cleveland, OH 44115-2214

Contributed by International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 21, 2012; final manuscript received June 30, 2012; published online October 25, 2012. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 134(12), 122509 (Oct 25, 2012) (6 pages) doi:10.1115/1.4007337 History: Received June 21, 2012; Revised June 30, 2012

This paper presents an experimentally driven model updating approach to address the dynamic inaccuracy of the nominal finite element (FE) rotor model of a machining spindle supported on active magnetic bearings. Modeling error is minimized through the application of a numerical optimization algorithm to adjust appropriately selected FE model parameters. Minimizing the error of both resonance and antiresonance frequencies simultaneously accounts for rotor natural frequencies as well as for their mode shapes. Antiresonance frequencies, which are shown to heavily influence the model’s dynamic properties, are commonly disregarded in structural modeling. Evaluation of the updated rotor model is performed through comparison of transfer functions measured at the cutting tool plane, which are independent of the experimental transfer function data used in model updating procedures. Final model validation is carried out with successful implementation of robust controller, which substantiates the effectiveness of the model updating methodology for model correction.

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References

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Figures

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Fig. 1

Top: spindle cross section. Note that the drawing does not include the tool holder. Bottom: spindle photo.

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Fig. 2

The FE rotor model with subregions designating the structurally uncertain elements

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Fig. 3

The open-loop model (solid lines)

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Fig. 4

Transfer functions from the front (top) and rear (bottom) AMBs illustrating the nominal model and experimental data

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Fig. 5

Transfer functions from the front (top) and rear (bottom) AMBs illustrating the updated model and experimental data

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Fig. 6

Mode shapes of the first two bending modes illustrating the updated model and the experimental data

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Fig. 7

Transfer functions from the front (top) and rear (bottom) AMBs illustrating the updated model (excluding antiresonances) and experimental data

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Fig. 8

Mode shapes of the first two bending modes for the updated model (excluding antiresonances) and the experimental data

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Fig. 9

Experimental and simulated stiffness of the spindle at the tool plane for the μ-controller and the PID controller

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